This project has been considering salamander neurulation as a model system for studying the mechanisms of epithelial cell shape determination during morphogenesis. Recent work focuses on those aspects of cell shape determination which are autonomous to the cell by considering isolated single cells in culture. In the coming year these studies will be completed and reported. They indicate that elongation of neural epithelial cells is autonomous, that it is unique to cells which elongate in vivo, and it appears to be independent of microtubule function. Time-lapse, electron-microscopic and assorted inhibitor studies of isolated cells are in progress. Further consideration of cell shape change will be continued on a new system: the elongation and contraction of photoreceptors in the teleost retina in response to light and dark adaptation. These shape changes will be characterized ultrastructurally and elongation and/or contraction will be considered in isolated retinas and in isolated photoreceptors. The major thrust of this work is to investigate possible control mechanisms for elongation and contraction, particularly the role of calcium.